Calpain inhibitors, but not caspase inhibitors, prevent actin proteolysis and DNA fragmentation during apoptosis.
Apoptosis, or programmed cell death, involves a cascade of regulatory events leading to the activation of specific proteases. However, the key substrates for these proteases remain to be identified. We previously demonstrated that levels of five unidentified polypeptides were specifically increased in neurons from embryonic chicken ciliary ganglia undergoing apoptosis by trophic deprivation. Here we show by microsequencing of two of these polypeptides that they are fragments of actin. One of them represents cleavage of actin at the site of interaction with DNase I. The same actin fragments are also found at early stages of apoptosis in chicken and rat dorsal root ganglion neurons, chicken spinal motoneurons and rat thymocytes. Actin fragmentation may play a role in the apoptotic process, since calpain inhibitors I and II both inhibit neuronal death and suppress actin fragmentation. In contrast, caspase (ICE family) inhibitors, though effective in delaying neuronal death, do not prevent actin cleavage or DNA fragmentation. These results indicate a key role for calpain-like proteases in neuronal programmed cell death and suggest that actin fragmentation in the cell is correlated with subsequent DNA fragmentation.
Villa
P G
PG
INSERM U.382, Developmental Biology Institute of Marseille, Campus de Luminy, Marseille, France.
Henzel
W J
WJ
Sensenbrenner
M
M
Henderson
C E
CE
Pettmann
B
B
D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002154:Calpain / Q000037:antagonists & inhibitors*; D002642:Chick Embryo; D002924:Ciliary Body / Q000294:innervation; D020934:Ciliary Neurotrophic Factor; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D053938:DNA Fragmentation / Q000187:drug effects*; D005726:Ganglia, Parasympathetic / Q000378:metabolism; D006023:Glycoproteins / Q000494:pharmacology; D006868:Hydrolysis / Q000187:drug effects; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017421:Sequence Analysis
D000199:Actins; D020934:Ciliary Neurotrophic Factor; D015853:Cysteine Proteinase Inhibitors; D006023:Glycoproteins; D009419:Nerve Tissue Proteins; D009842:Oligopeptides; D010446:Peptide Fragments; C039304:calpain inhibitors; C069861:calpain inhibitor 2; D002154:Calpain